How to Calculate Flow Rate 3d Printer

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3D Printer Flow Rate Calculator

Measure the actual thickness of your printed single-wall cube with calipers.

Recommended Flow Rate:

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Update this value in your slicer settings (Extrusion Multiplier).

function calculateFlowRate() { var measured = parseFloat(document.getElementById('measuredWall').value); var expected = parseFloat(document.getElementById('expectedWall').value); var current = parseFloat(document.getElementById('currentFlow').value); var resultBox = document.getElementById('flowResult'); var resultValue = document.getElementById('resultValue'); if (isNaN(measured) || isNaN(expected) || isNaN(current) || measured <= 0 || expected <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Formula: (Expected / Measured) * Current var newFlow = (expected / measured) * current; resultValue.innerHTML = newFlow.toFixed(2) + "%"; resultBox.style.display = 'block'; }

How to Calculate Flow Rate for Your 3D Printer

Flow rate, also known as the Extrusion Multiplier in slicers like Cura, PrusaSlicer, or Bambu Studio, determines how much plastic the extruder pushes out. If your flow rate is off, you will experience dimensional inaccuracies, gaps between lines (under-extrusion), or blobs and stringing (over-extrusion).

The Flow Rate Calibration Formula

To calculate your new flow rate, you need to compare what your slicer expected to print versus what your printer actually printed. The mathematical formula is:

New Flow Rate = (Expected Wall Thickness / Measured Wall Thickness) * Current Flow Rate

Step-by-Step Calibration Guide

  1. Print a Calibration Cube: Design or download a simple 20x20mm cube. In your slicer, set it to "Vase Mode" (Spiralize Outer Contour) with 0 top layers and 0% infill.
  2. Check Your Settings: Note your "Line Width" or "Extrusion Width" in the slicer. For a 0.4mm nozzle, this is typically 0.40mm or 0.45mm. This is your Expected Wall Thickness.
  3. Measure the Walls: Use digital calipers to measure the thickness of the printed wall on all four sides. Average these four measurements to get your Measured Wall Thickness.
  4. Input Data: Enter your measurements into the calculator above to find your optimized flow percentage.
  5. Update Slicer: Enter the result into the "Flow Rate" or "Extrusion Multiplier" field in your slicer and run a test print.

Example Calculation

Imagine you are printing with a Current Flow Rate of 100%. Your slicer is set to a 0.40mm Line Width, but when you measure the wall with calipers, it actually measures 0.44mm.

Using the formula: (0.40 / 0.44) * 100 = 90.91%. You would change your flow rate to 91% to achieve perfect dimensional accuracy.

Why Calibration is Necessary

Different filaments (PLA, PETG, ABS, TPU) have different viscosities and diameters. Even two rolls of PLA from different brands can require different flow rates. Performing this calibration for every new brand of filament ensures that your parts fit together perfectly every time.

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